1. Technical Field
The present invention relates generally to a process applicable to the recycling and recovering of minerals and more particularly to a process for recovering minerals from waste streams. The present invention additionally relates generally to a method for the evaluation and recycling of various waste streams by recovering economically valuable minerals and more particularly to a process for recovering economically valuable minerals from waste and other carpet and from other post-consumer/post-industrial waste streams. This invention further relates to the recovery of energy from a process for recycling and recovering minerals.
2. Prior Art
As stated above the present invention is applicable to the production of post-consumer (PC) and post-industrial (PI) products in general from a wide variety of sources; however, a preferred embodiment of the present invention relates to the use of carpet third stream, carcasses, whole carpet, and/or other waste carpet materials as the source of post-consumer and post-industrial fillers and energy.
Used and discarded carpet is a potentially valuable resource. Typical whole carpet construction contains various fiber types that are tufted into a primary backing that is bound as a structural system by a backcoating. Primary and secondary backcoatings contain various polymers and fillers, such as SBR, EVA, PET, PVC, calcium carbonate, clay and glass. In simple terms, the face of carpet is woven through a backing fabric and held in place by an “adhesive” which is often a latex cross-linked polymer or thermoresin loaded with calcium carbonate and/or other mineral filler materials.
The term third stream as frequently used in connection with PC and PI materials, or recycling, in general, refers to a stream of recovered materials containing the highest concentrations of fillers and binders, and, optionally, filler wetting agents, which are extracted from the recycling of whole carpet and the recovery of energy. The third stream is exothermic in nature.
U.S. Pat. No. 5,908,701 teaches the three stream concept in which the first stream reacts with the second stream and the third stream contains filler or fillers.
These petroleum and bio based polymers and mineral fillers can potentially be recovered and reused. Polymeric fibers are being selectively recovered from PI and PC carpet employing grinding and shaving techniques. Carcasses, remnants of the backing structure once the fiber has been shaved off, and the third stream as described earlier are two of the major streams considered of less value in carpet recycling. Other recovery techniques include the processing of the carpet into the caprolactam-monomer process with nylon 6 as the feedstock. The recovered fibers, known as fluff, and caprolactam have value as thermo-plastic resins and fiber resource materials in a range of applications.
It is generally thought that carpet backing has little value as a recycled material and certainly less value than the recovered polymers. Carpet backing is roughly 50% of the weight of whole carpet. It is also generally considered that wet and dirty whole carpet has little value. Wet and dirty whole carpet are not considered priority options when processing “fluff” and caprolactam. Carpet is bulky, difficult to handle and to ship, and in all cases must be kept dry for traditional recycling. Still, it is generally recognized that it would be a significant benefit to the public to keep carpet out of the landfills.
Bell teaches mechanically reducing the size of carpet to the size of calcium carbonate typically used as a filler. U.S. Pat. Nos. 7,045,590 and 6,786,988 and US Patent Publication No. 20050209439 further disclose the incorporation of such fragments in carpet backings. The resulting filler is composed of mineral filler and some resulting fibers due to the challenges of mechanically separating and liberating the fibers and binders from the mineral filler. The final product has limited applications as a stand-alone product due to the physical attributes, composition and chemistry of the recovered materials.
US Patent Publication No. 20100330288 discloses a method for reclaiming inorganic filler from waste carpeting, comprising the steps providing a waste carpeting composition comprising an inorganic filler component and an organic component, and heat treating the waste carpeting composition under conditions effective to separate at least a portion of the organic component from the waste carpeting composition and to provide a reclaimed inorganic filler composition at least substantially free of the organic component, but does not contemplate sufficiently treating the reactants so as to result in a mineral product having the desired features.
US Patent Publication No. 20100044480 and U.S. Pat. No. 7,635,099 respectively focus on mechanical separation and liberation. US Patent Publication No. 20100044480 recognizes the limitations of mechanical separation and introduces a thermal step that attempts to separate more of the fibers. US Patent Publication No. 20100044480 discloses a recovery process for recovering filler material from carpet waste comprising providing carpet; size-reducing the carpet waste into particulate matter comprising polymer fibers, filler material and adhesive material; separating the particulate matter into a first stream comprising substantially polymer fibers and a second stream comprising substantially filler material and adhesive material; and heating the second stream at a temperature sufficient to remove at least some of the polymer fibers remaining in the second stream to enrich the content of filler material in the second stream. U.S. Pat. No. 7,635,099 discloses a component recovery process comprising providing a material feed including fiber, filler and adhesive; shredding the material feed to liberate filler and adhesive from the fiber; screening the shredded material feed yielding at least two resultant streams, a first of which comprises fiber suitable for depolymerization feed stocks and a second of which comprises filler suitable for direct reinforcement in polymer resins; combining the first resultant stream with a liquid to form a slurry; and centrifuging the slurry at a G-Force of 30 G or less.
U.S. Pat. No. 5,728,741 teaches mechanically reducing the waste polymeric materials to 100 times smaller than the waste polymeric material presented and then extruding it for use.
A DOE report entitled “Carpet As An Alternative Fuel in Cement Kilns” (DOE/CH/112390) sets forth the benefits and many problems associated with this approach. Related papers discuss specific aspects of this approach: “A Pilot-Scale Study on the Combustion of Waste Carpet in a Rotary Kiln: Dioxin and Furan Emissions” by Lemieux et al. (IT 32005 Conference) and “Characterization of Transient Puff Emissions from the Burning of Carpet Waste Charges in a Rotary Kiln Combustor” by Realff et al. (Cement Technical Conference, May 2005).
US Patent Publication No. 20090017253 discloses collecting waste carpeting (post-consumer and/or waste from new carpet manufacture) containing calcium carbonate and a thermoplastic resin and size-reducing the waste to a size corresponding to the size of calcium carbonate typically used as a filler. The size-reduced waste carpeting is added as filler to at least one other material, such as polymers in standard latex, EVA, or PVC carpet backcoatings, to provide a composite material, and then the composite is used to make the useful product (such as carpet backcoating, which is used as a primary or secondary backcoating in the manufacture of new carpeting). The invention is a method of recycling waste carpeting and forming a new carpet containing the recycled waste carpeting comprising: collecting waste carpeting containing thermoset materials; processing the waste carpeting to provide a first material from the waste carpeting containing the thermoset materials and reducing the first material to a predetermined size in a range of 50-100 to 95-325 mesh size; adding the first material to a second material to provide a composite material useful in the manufacture of the new carpet; and making the new carpet containing the composite material.
US Patent Publication No. 20090300982 discloses concentrating the calcium carbonate component of waste carpet by mechanical and/or chemical means, then subjecting the calcium carbonate to a heat treatment at a temperature below the decomposition temperature of calcium carbonate to volatilize or modify organic compounds admixed with calcium carbonate so as to yield a free-flowing particulate filler composed of at least about 70% calcium carbonate. The invention is a method for preparing a free-flowing particulate filler material composed predominantly of calcium carbonate from a backing component of waste carpeting containing calcium carbonate useful as a filler material in industrial applications comprising: collecting waste carpeting; separating a backing component containing calcium carbonate from the face fiber component of the collected waste carpeting by subjecting the collected waste carpeting to one or more mechanical comminution processes followed by one or more physical separation processes to separate the collected waste carpeting into at least two physically and chemically distinct fractions, one of which contains substantially all of the backing, or one or more chemical processes to render one or more polymeric components of the face fibers in the collected waste carpet separable from the backing component of the collected waste carpet including dissolution or depolymerization of one or more polymeric components of the face fiber component of the collected waste carpeting, followed by separation of the one or more polymeric components of the face fibers in the collected waste carpet from the backing component of the collected waste carpeting or a combination of mechanical and chemical processes to separate the collected waste carpeting into at least two fractions, one of which contains substantially all of the backing component from the collected waste carpeting; and heating the backing component from the collected waste carpeting to a temperature above about 400° C. but below about 800° C. for a time sufficient to remove substantially all volatile organic compounds from the backing component of the aforesaid collected waste carpeting.
Some have concluded that it is not economically feasible to find markets for over half of the materials in the carpet waste stream. (The Waste to Energy Workshop Group).
Therefore, it can be seen that there has long existed a need for an integrated process which provides for the recovery of the minerals, such as fillers and pigments, in a form and under conditions which will allow them to be reused in the same or related systems from which they were derived, and for the recovery of the energy value of the organic portion of waste streams, which has been unfulfilled prior to the invention of the present process.